Field of the Invention
This invention relates to an independent wheel suspension with a toe correcting link.
Disclosure Information
The three principal attitude measurements of vehicle road wheels are caster, camber, and toe. This invention is concerned with the control of toe angle during braking, and off throttle operation. Vehicles equipped with solid beam type rear drive axles do not present designers with any particular difficulty in terms of the need to control the toe angle of the rear driving wheels during various vehicle operating modes. With the advent, however, of independent rear suspensions for driving wheels, the need has arisen for controlling toe angle so as to provide safe operation of vehicles equipped with independent suspensions because it is well known that if uncontrolled, or under controlled, rear wheel toe angle may cause steering to be unpredictable.
Automotive designers have attempted a number of solutions for the problems posed by the need to control toe during various vehicle operating modes. U.S. Pat. No. 3,893,701 discloses an independent suspension in which one guide arm consisting of a leaf spring elastically allows toe in during cornering. The elastic guide arm is further said to prevent toe changes during braking and acceleration. This system is not susceptible to simple adjustment of the toe control, however, because the leaf spring element must be changed to accomplish any adjustment.
U.S. Pat. No. 4,491,341 discloses an independent rear suspension having a semi-trailing arm and MacPherson strut with toe control provided by a transversely extending control rod. This system is said to produce toe in during turning movements and deceleration of the vehicle.
U.S. Pat. No. 4,457,536 discloses an independent rear wheel suspension for a motor vehicle in which the toe angle of a wheel carrier attached to a first laterally extending control arm is controlled during jounce and recession by means of a second laterally extending control arm mounted rearwardly of the first arm.
U.S. Pat. No. 4,456,282 discloses an independent rear wheel suspension for a front drive vehicle in which the toe angle of the wheel carrier is controlled during recession by a trailing arm having an inwardly angled attachment at its leading end.
U.S. Pat. No. 4,462,609 discloses an independent suspension for rear drive vehicle including upper and lower wishbone-shaped control arms and a generally transverse track rod. This system translates limited rotation of the wheel carrier about the roadwheel's rotational axis into toe-in during braking as well as other vehicle operating modes. It has been found, however, that this configuration is particularly sensitive to changes in location of the pivot points of the upper control arm with respect to the pivot points of the lower control arm. This sensitivity could present problems during mass production of a vehicle having this suspension.
U.S. Pat. No. 3,202,237 discloses an independent suspension which will produce toe in during jounce movement of the wheel assembly but will allow toe out during braking and throttle-off operation.
U.S. Pat. No. 4,181,322 discloses an independent rear suspension having a rear guide rod arm comprising a leaf spring extending generally transversely of the vehicle and a longitudinal strut member elastically supported on a rotating shaft by means of an elastic bushing interposed between a sleeve carried upon the longitudinal strut member and the rotating bearing shaft. This arrangement is said to control wheel camber changes during braking and acceleration.
U.S. Pat. No. 3,111,307 discloses a semi-trailing arm independent suspension in which a lower control arm is mounted with the roller cam at its leading end, which allows recession in the event that the road wheel strikes an obstruction. There is no suggestion that movement of the lower control arm affects the toe angle of the wheel carrier or road wheel.
U.S. Pats. Nos. 4,245,853 and 4,269,432 discloses an independent wheel suspension in which separate front and rear control arms individually pivoted to a wheel carrier produce toe in during wheel recession.
U.S. Pat. No. 4,478,430 discloses a turnable arm suspension system which produces toe in during suspension jounce, but which would likely exhibit toe-out during wheel recession.
Finally, as shown in Automobiltechnische Zeitschrift 84 (1982) 7/8, BMW automobile models 733i/528i use a screw-motion, semi-trailing arm rear axle having a auxiliary linkage between the outboard mounting of the trailing arm and the chassis which produces toe in by manipulating the trailing arm during jounce and rebound motion of the suspension but not during recession.
It is an object of the present invention to provide an independent suspension for driven or non-driven wheels in which the toe angle is controlled solely by action of the lower control arm and its related toe correcting link and not by the action of an upper control arm.
It is a further of the invention to provide a suspension arrangement which is relatively insensitive to variations and locations of the upper pivot points with respect to the lower pivot points in terms of the ability to control toe angle during wheel recession.
It is yet another object of the present invention to provide an independent wheel suspension which has the capability of providing toe in during wheel recession including braking and off-throttle operation as well as in response to wheel recession from impacts with obstructions in the roadway.
It is yet another object of the present invention to provide a suspension arrangement having readily adjustable toe control.